States file a joint lawsuit over changes to post office operations.

Six states and the District of Columbia sued the Postal Service and the postmaster general on Friday, alleging that recent operational and policy changes were illegal and “designed to undermine” the agency’s ability to operate effectively as millions of Americans plan to vote by mail during the pandemic.

The lawsuit was announced as Postmaster General Louis DeJoy testified before a Senate committee about the operation and integrity of the Postal Service.

Facing backlash over concerns that cost-cutting measures were slowing the mail and could imperil the November election, Mr. DeJoy had announced on Tuesday that the Postal Service would suspend operational changes until after the election.

But in announcing Friday’s lawsuit, Josh Shapiro, the Pennsylvania attorney general, asserted that Mr. DeJoy had not addressed some of the lawsuit’s core concerns and called for “detailed information” on how the agency would reverse what he said were “illegal changes.”